Preparation method of degradable packaging bag

Abstract

A preparation method of a degradable packaging bag belongs to the technical field of plastic products, and comprises the following steps: adding hexamethylene diisocyanate into a cellulose nanocrystal dispersion liquid, and reacting in an inert atmosphere to obtain isocyanate modified cellulose nanocrystals; mixing the isocyanate modified cellulose nanocrystals with 1, 4-butanediol, carrying out ultrasonic treatment, carrying out stirring reaction in an inert atmosphere to obtain slurry, mixing the slurry with succinic acid, carrying out esterification reaction and polycondensation reaction to obtain a polymer, and carrying out hot press molding on the polymer to obtain the packaging bag. According to the method, the cellulose nanocrystals are subjected to surface modification through isocyanate, the dispersity of the cellulose nanocrystals is improved, and meanwhile, the isocyanate modified cellulose nanocrystals participate in polymerization of 1, 4-butanediol and succinic acid, so that high-performance nano-modified poly (butylene succinate) is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of plastic products, and particularly relates to a preparation method of a degradable packaging bag. Background Art

[0002] A packaging bag refers to a bag used for packaging various articles, which facilitates the transportation and storage of goods during the production and circulation process. Among them, plastics are widely used in the packaging field due to their advantages such as light weight, high strength, good processability, and low price. However, since a large number of plastic packaging bags are discarded casually after use, these plastic wastes are difficult to degrade in the natural environment. Accumulated over a long time, they not only occupy precious land resources but also seriously damage the ecological balance.

[0003] Biodegradable plastics can be completely degraded into carbon dioxide (CO2), water, methane, mineralized inorganic salts, etc. by the action of microorganisms existing in nature under natural or specific conditions. The substitution of traditional plastic packaging bags with biodegradable plastic packaging bags has become one of the important ways to solve plastic pollution.

[0004] At present, there is still a certain gap between commonly used commercially available biodegradable plastics and traditional plastics in terms of mechanical properties and barrier properties, which limits the application of biodegradable plastics in packaging bags. Summary of the Invention

[0005] In view of the above situation, in order to overcome at least some of the above-mentioned defects of the prior art, the present invention provides a preparation method of a degradable packaging bag.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a preparation method of a degradable packaging bag, which is characterized by comprising: Adding hexamethylene diisocyanate to a cellulose nanocrystal dispersion liquid, and reacting under an inert atmosphere to obtain isocyanate-modified cellulose nanocrystals; Mixing the isocyanate-modified cellulose nanocrystals and 1,4-butanediol, performing ultrasonic treatment, and stirring and reacting under an inert atmosphere to obtain a slurry. After mixing the slurry and succinic acid, performing an esterification reaction and a polycondensation reaction to obtain a polymer, and performing hot pressing on the polymer to obtain a packaging bag.

[0007] In some embodiments, the temperature of the reaction under an inert atmosphere is 30°C - 40°C, and the time is 20h - 30h.

[0008] In some embodiments, in the cellulose nanocrystal dispersion liquid, the mass fraction of cellulose nanocrystals is 5% - 8%; and / or, the solvent of the cellulose nanocrystal dispersion liquid is toluene.

[0009] In some embodiments, the volume ratio of the cellulose nanocrystal dispersion to hexamethylene diisocyanate is 20:(1-2).

[0010] In some embodiments, the mass ratio of the isocyanate-modified cellulose nanocrystals to 1,4-butanediol is (1-5):40 when they are mixed.

[0011] In some embodiments, the time for ultrasonic treatment is 20 min - 40 min, and the power is 100 W - 200 W.

[0012] In some embodiments, the temperature of the stirring reaction is 80°C - 90°C, the time is 1 h - 2 h, and the stirring speed is 100 rpm - 200 rpm.

[0013] In some embodiments, the mass ratio of the slurry to succinic acid is 1:1.1 - 1.2 when they are mixed.

[0014] In some embodiments, the temperature of the esterification reaction is 160°C - 190°C, and the time is 3 h - 5 h.

[0015] In some embodiments, the temperature of the polycondensation reaction is 230°C - 250°C, and the time is 2 h - 4 h.

[0016] The beneficial effects achieved by the present invention are as follows: The surface of cellulose nanocrystals is modified by isocyanate to improve the dispersibility of cellulose nanocrystals. At the same time, the isocyanate-modified cellulose nanocrystals participate in the polymerization of 1,4-butanediol and succinic acid, thereby preparing a high-performance nano-modified poly(butylene succinate). Compared with the prior art, the packaging bags based on poly(butylene succinate) have poor mechanical properties and barrier properties. The packaging bags prepared by the method of the present invention not only have excellent degradability, but also have high mechanical properties and barrier properties. Detailed Embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are only for illustrative purposes and do not limit the content of this application.

[0019] In view of the deficiencies in the prior art mentioned in the background art, an embodiment of the present invention provides a method for preparing a degradable packaging bag, which is characterized by including: Adding hexamethylene diisocyanate to the cellulose nanocrystal dispersion and reacting under an inert atmosphere to obtain isocyanate-modified cellulose nanocrystals; Mixing the isocyanate-modified cellulose nanocrystals and 1,4-butanediol, performing ultrasonic treatment, and stirring and reacting under an inert atmosphere to obtain a slurry. After mixing the slurry and succinic acid, through esterification reaction and polycondensation reaction, a polymer is obtained, and the polymer is hot-pressed into a packaging bag.

[0020] Cellulose nanocrystals are natural nanomaterials extracted from cellulose, with a large specific surface area, high structural stiffness, and good biocompatibility. However, due to incompatibility with hydrophobic polymers, the application of cellulose nanocrystals in enhancing polymers is limited. Hexamethylene diisocyanate can react with the hydroxyl groups of cellulose nanocrystals to prepare isocyanate-modified cellulose nanocrystals with isocyanate groups on the surface, improving the compatibility between cellulose nanocrystals and hydrophobic polymers. At the same time, the isocyanate-modified cellulose nanocrystals can participate in the polymerization of 1,4-butanediol and succinic acid, thereby improving the performance of polybutylene succinate, and further a packaging bag with excellent degradability, high mechanical properties, and strong barrier properties can be prepared.

[0021] Among them, the isocyanate groups of the isocyanate-modified cellulose nanocrystals can react with the hydroxyl groups of 1,4-butanediol, thereby grafting 1,4-butanediol, and then a prepolymer is prepared through an esterification reaction, and finally a high-molecular-weight polymer is prepared through a polycondensation reaction.

[0022] Preferably, the inert atmosphere is at least one of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

[0023] Preferably, the temperature of the hot pressing is 140°C - 150°C, the heat preservation time is 5 min - 10 min, and the pressure is 40 MPa - 50 MPa.

[0024] In some embodiments, the temperature of the reaction under an inert atmosphere is 30°C - 40°C, and the time is 20 h - 30 h. Controlling the temperature of the reaction under an inert atmosphere at 30°C - 40°C can promote the reaction between isocyanate groups and hydroxyl groups, and controlling the time at 20 h - 30 h can enable the reaction between isocyanate groups and hydroxyl groups to proceed fully, improving the yield of the isocyanate-modified cellulose nanocrystals.

[0025] In some embodiments, in the cellulose nanocrystal dispersion, the mass fraction of cellulose nanocrystals is 5% - 8%. The cellulose nanocrystal dispersion with a mass fraction of 5% - 8% has good dispersion stability and uniformity, which is beneficial to the dispersion of cellulose nanocrystals.

[0026] In some embodiments, the solvent of the cellulose nanocrystal dispersion is toluene. Toluene has moderate volatility and high chemical stability, and is not prone to side reactions or thermal decomposition, which can provide a relatively stable reaction environment.

[0027] In some embodiments, the volume ratio of the cellulose nanocrystal dispersion to hexamethylene diisocyanate is 20:(1 - 2). By setting the volume ratio of the cellulose nanocrystal dispersion to hexamethylene diisocyanate to 20:(1 - 2), the hexamethylene diisocyanate can come into full contact with the hydroxyl groups on the surface of the cellulose nanocrystals, which is beneficial to the progress of the reaction.

[0028] In some embodiments, the mass ratio of the isocyanate-modified cellulose nanocrystals to 1,4-butanediol is (1 - 5):40. By setting the mass ratio of the isocyanate-modified cellulose nanocrystals to 1,4-butanediol to (1 - 5):40, the isocyanate groups of the isocyanate-modified cellulose nanocrystals can fully react with the hydroxyl groups of 1,4-butanediol, and a part of 1,4-butanediol is reserved to participate in the subsequent esterification reaction and polycondensation reaction.

[0029] In some embodiments, the time of ultrasonic treatment is 20 min - 40 min, and the power is 100 W - 200 W. Ultrasonic treatment can make the isocyanate-modified cellulose nanocrystals uniformly dispersed in 1,4-butanediol. Setting the time of ultrasonic treatment to 20 min - 40 min and the power to 100 W - 200 W can further promote the dispersion of the isocyanate-modified cellulose nanocrystals, and at the same time avoid excessive ultrasonic treatment and damage to the structure of the isocyanate-modified cellulose nanocrystals.

[0030] In some embodiments, the temperature of the stirring reaction is 80°C - 90°C, the time is 1 h - 2 h, and the stirring speed is 100 rpm - 200 rpm. Stirring can make the isocyanate-modified cellulose nanocrystals and 1,4-butanediol come into full contact during the reaction process, thereby increasing the reaction rate. At the same time, setting the temperature to 80°C - 90°C and the time to 1 h - 2 h can make the isocyanate-modified cellulose nanocrystals and 1,4-butanediol react fully.

[0031] In some embodiments, the mass ratio of the slurry to succinic acid is 1:1.1 - 1.2. By setting the mass ratio of the slurry to succinic acid to 1:1.1 - 1.2, the succinic acid can react completely with the slurry, increasing the polymer yield. At the same time, it can avoid excessive accumulation of succinic acid and hinder the reaction.

[0032] In some embodiments, the temperature of the esterification reaction is 160°C - 190°C and the time is 3h - 5h. The esterification reaction of 1,4-butanediol and succinic acid can produce a prepolymer. By setting the temperature of the esterification reaction to 160°C - 190°C and the time to 3h - 5h, it is beneficial to the progress of the esterification reaction.

[0033] In some embodiments, the temperature of the polycondensation reaction is 230°C - 250°C and the time is 2h - 4h. A high-molecular-weight polybutylene succinate can be obtained through the polycondensation reaction. By setting the temperature of the polycondensation reaction to 230°C - 250°C and the time to 2h - 4h, it is beneficial to the progress of the polycondensation reaction. Preferably, the polycondensation reaction is carried out under vacuum conditions, so that the by-products (such as alcohols and water) of the polycondensation reaction can be removed in time, and the molecular weight of the polymer can be increased.

[0034] The present invention will be further described below by way of specific embodiments.

[0035] The experimental methods in the following examples are all conventional methods unless otherwise specified; the test materials used in the following examples are all obtained by purchasing from commercial channels unless otherwise specified.

[0036] Example 1 Hexamethylene diisocyanate was added to a 5% mass fraction cellulose nanocrystal - toluene dispersion. The volume ratio of the cellulose nanocrystal dispersion to hexamethylene diisocyanate was 20:1. The reaction was carried out under an inert atmosphere of nitrogen at a temperature of 30°C for 20h to obtain isocyanate-modified cellulose nanocrystals; The isocyanate-modified cellulose nanocrystals and 1,4-butanediol were mixed. The mass ratio of the isocyanate-modified cellulose nanocrystals to 1,4-butanediol was 1:40. Ultrasonic treatment was carried out for 20 min at a power of 100 W. The reaction was stirred under a nitrogen atmosphere at a temperature of 80°C for 1 h at a stirring speed of 100 rpm to obtain a slurry. After the slurry and succinic acid were mixed, the mass ratio of the slurry to succinic acid was 1:1.1. Through the esterification reaction and the polycondensation reaction, the temperature of the esterification reaction was 160°C and the time was 3 h, and the temperature of the polycondensation reaction was 230°C and the time was 2 h to obtain a polymer. The polymer was hot-pressed into a packaging bag.

[0037] Example 2 Hexamethylene diisocyanate was added to an 8% mass fraction cellulose nanocrystal - toluene dispersion. The volume ratio of the cellulose nanocrystal dispersion to hexamethylene diisocyanate was 20:2. The reaction was carried out under an inert atmosphere of nitrogen at a temperature of 40°C for 30h to obtain isocyanate-modified cellulose nanocrystals; Mix isocyanate-modified cellulose nanocrystals and 1,4-butanediol. The mass ratio of isocyanate-modified cellulose nanocrystals to 1,4-butanediol is 5:40. Conduct ultrasonic treatment for 40 min at a power of 200 W. Stir and react under a nitrogen atmosphere at 90 °C for 2 h with a stirring speed of 200 rpm to obtain a slurry. After mixing the slurry and succinic acid, the mass ratio of the slurry to succinic acid is 1:1.2. Through esterification reaction and polycondensation reaction, the temperature of the esterification reaction is 190 °C for 5 h, and the temperature of the polycondensation reaction is 250 °C for 4 h to obtain a polymer. Then, hot press the polymer to obtain a packaging bag.

[0038] Example 3 Consistent with Example 1, except that the mass ratio of isocyanate-modified cellulose nanocrystals to 1,4-butanediol is 2:40.

[0039] Example 4 Consistent with Example 1, except that the mass ratio of isocyanate-modified cellulose nanocrystals to 1,4-butanediol is 3:40.

[0040] Example 5 Consistent with Example 1, except that the mass ratio of isocyanate-modified cellulose nanocrystals to 1,4-butanediol is 4:40.

[0041] Example 6 Consistent with Example 1, except that the mass ratio of isocyanate-modified cellulose nanocrystals to 1,4-butanediol is 5:40.

[0042] Example 7 Consistent with Example 1, except that the mass ratio of the slurry to succinic acid is 1:1.15.

[0043] Example 8 Consistent with Example 1, except that the mass ratio of the slurry to succinic acid is 1:1.2.

[0044] Comparative Example 1 Consistent with Example 1, except that cellulose nanocrystals are used instead of isocyanate-modified cellulose nanocrystals.

[0045] Comparative Example 2 Consistent with Example 1, except that isocyanate-modified cellulose nanocrystals are not added.

[0046] Conduct performance tests on the packaging bags prepared in Examples 1-8 and Comparative Examples 1 and 2. The specific test contents are as follows: Mechanical property test: The tensile strength of the packaging bag was measured using an electronic fabric strength tester. The test sample was cut into rectangular strips of 1 cm × 8 cm for testing. The tensile rate was 10 mm / min, and the initial probe spacing was 20 mm.

[0047] Oxygen barrier property test: The oxygen permeability coefficient was measured using a VAC-VBS differential pressure gas permeation instrument at a relative humidity of 50% as follows: A thin layer of vacuum grease was applied to the convex edge of the gas permeation chamber. The sample cut into a diameter of 95 mm was pressed tightly against the vacuum grease to avoid sample wrinkles. The gas permeation chamber lid was tightened. The oxygen flow rate was adjusted so that the exhaust pressure was between 0.5 MPa and 0.6 MPa. After the vacuuming was completed, the instrument automatically entered the test stage to obtain the results.

[0048] Degradation performance test: Biodegradation test was carried out by landfill degradation method. The sample was taken out after 60 days of landfill and its remaining mass was measured and the degradation rate was calculated. Degradation rate = (mass before degradation - remaining mass) / mass before degradation × 100%.

[0049] The test results are shown in Table 1.

[0050] Table 1 Test results

[0051] It can be seen from Table 1 that the mechanical properties and barrier properties of Example 1 are significantly improved compared with Comparative Example 1 and Comparative Example 2. This is because isocyanate modifies the surface of cellulose nanocrystals, improving the dispersibility of cellulose nanocrystals. At the same time, isocyanate-modified cellulose nanocrystals can participate in the polymerization of 1,4-butanediol and succinic acid, improving the mechanical properties and barrier properties of the packaging bag. And the degradation rate of Example 1 is significantly improved compared with Comparative Example 2 and has no significant change compared with Comparative Example 1. It can be seen that the addition of cellulose nanocrystals can improve the degradation rate of the packaging bag, and isocyanate-modified cellulose nanocrystals do not significantly affect the degradability of cellulose nanocrystals.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the protection scope of the present invention.

Claims

1. A preparation method of a degradable packaging bag, characterized in that, Including: Adding hexamethylene diisocyanate to the cellulose nanocrystal dispersion and reacting under an inert atmosphere to obtain isocyanate-modified cellulose nanocrystals; Mixing the isocyanate-modified cellulose nanocrystals and 1,4-butanediol, performing ultrasonic treatment, stirring and reacting under an inert atmosphere to obtain a slurry. After mixing the slurry and succinic acid, through esterification reaction and polycondensation reaction, a polymer is obtained, and the polymer is hot-pressed into a packaging bag.

2. The preparation method according to claim 1, wherein The temperature of the reaction carried out under an inert atmosphere is 30°C - 40°C, and the time is 20h - 30h.

3. The preparation method according to claim 1, wherein In the cellulose nanocrystal dispersion, the mass fraction of cellulose nanocrystals is 5% - 8%; and / or, the solvent of the cellulose nanocrystal dispersion is toluene.

4. The preparation method according to claim 1, wherein, The volume ratio of the cellulose nanocrystal dispersion to hexamethylene diisocyanate is 20:(1 - 2).

5. The preparation method according to claim 1, wherein The mass ratio of the isocyanate-modified cellulose nanocrystals to 1,4-butanediol in the mixture is (1 - 5):

40.

6. The preparation method according to claim 1, characterized in that, The time of the ultrasonic treatment is 20min - 40min, and the power is 100W - 200W.

7. The preparation method according to claim 1, characterized in that, The temperature of the stirring reaction is 80°C - 90°C, the time is 1h - 2h, and the stirring speed is 100rpm - 200rpm.

8. The preparation method according to claim 1, wherein The mass ratio of the mixture of the slurry and succinic acid is 1:1.1 - 1.

2.

9. The preparation method according to claim 1, characterized in that The temperature of the esterification reaction is 160°C - 190°C, and the time is 3h - 5h.

10. The preparation method according to claim 1, wherein, The temperature of the polycondensation reaction is 230°C - 250°C, and the time is 2h - 4h.

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